In conventional sewage systems the flush or transport medium is water. Water represents 90 to 98 percent of the total volume of the sewage handled in conventional systems. If a reusable flush medium is used, which may be readily separated from the sewage wastes, a more compact and efficient sewage system results. When the terms "sewage" or "waste" are used herein they are meant to describe any of the typical forms of waste matter generally encountered in sewage handling systems, including human excreta, paper, cigarette butts and the like.
Systems with reusable flush media have been previously proposed wherein the flush media is of a density different from that of the sewage. U.S. Pat. No. 3,673,614, issued July 4, 1972 to Robert W. Claunch and assigned to the same assignee as the subject application, describes such a system which has been successfully developed and is presently in use. The system described in that patent eliminates the use of water as a flush medium for sewage wastes and substitutes a reusable medium. The reusable flush medium is substantially immiscible with water and of a sufficient difference in density from that of water and other sewage wastes to permit physical separation of the sewage from the flush medium. It is also chemically stable under the operating conditions of the sewage facility and in the presence of sewage waste.
In the patented system, the flush medium is supplied to a point of use, such as an ordinary toilet commode or urinal, then flushed with any waste received through a sewer line into a separating tank. In the separating tank, due to its difference in density, the flush medium rises above the waste to float on it and an interface forms therebetween at the point of contact between the medium and the sewage waste.
Liquid flush medium floating on the waste in the separating tank is preferably passed through a suitable filter means and into a fluid circulation system for reuse. The circulation system preferably includes a pressurized storage tank or accumulator equipped with a pressure switch means which automatically activates a pump in the circulation system when the pressure in the accumulator drops below a pre-set minimum.
The waste collects at the bottom of the separating tank until a sufficient quantity has accumulated to activate an automatic transfer means. Waste is then transferred from the separating tank into a waste receiving means, such as a catch tank, holding tank, incinerator, aerobic digestor or the like. After a given quantity of the waste has been transferred the transfer means automatically stops and the accumulation of waste in the lower part of the separating tank starts again.
The transfer means prevents carryover of sewage waste with the flush medium when it is removed from the separating tank for reuse. It also controls the volume of waste allowed to collect in the separating tank. An electrical control system including floats and switches is used in the patented system to activate the transfer means at appropriate times for controlling the volume of waste and flush medium retained in the separating tank.